New Town: Palm, coconut, cherry blossom and more such slender trees are being planted across New Town.

The New Town Kolkata Development Authority (NKDA) has decided to change the way it plants trees in the township after hundreds of trees toppled over in Calcutta and Salt Lake during a thunderstorm that lashed the city on April 17.

Trees that spread out in a large canopy are being avoided as they are susceptible to being uprooted during storms if not pruned properly.

Naturalists say trees topple easily in Calcutta because of too much of concretisation around them. Trees need soil around them for the surface roots to grow. Along with the roots that penetrate into the soil, the surface roots, too, aid a tree to stand tall. If the area around a tree is concreted, the surface roots often fail to grow, a naturalist said.

"The base of the trees must not be concreted and soil must be left at their base to ensure that they don't come crashing down," said Raju Das, the managing director of the forest department-run West Bengal Wasteland Development Corporation Ltd.

An NKDA official said the trees planted in New Town had enough soil around them. "That is why fewer trees were uprooted in New Town during the thunderstorm," he said.

New Town roads have wide median dividers with a variety of trees. The NKDA will now focus on slender trees whose canopies are not that large, including cherry blossom or rosy trumpet, pine or casuarina, palm and coconut trees.

"We will source the trees from the Tall Tree Nursery jointly run by Hidco and the wasteland corporation in New Town's Action Area I," the official said.

Besides being at risk of toppling over, trees with large canopies also block light from streetlamps and obstruct motorists' vision.

Debashis Sen, the chairman of NKDA, said experts would be engaged to test the soil before planting suitable trees. More than 1,65,000 trees have already been planted in the township over the past couple of years.

"The initial findings of a survey conducted by the forest department have revealed that around 15 per cent of the trees have not survived and we will replace them with saplings that are at least three-four feet tall and have a higher chance of survival," Sen said.

Cherry blossoms planted along the boulevard outside Eco Park have done particularly well, an NKDA official said.

There are several plantations of palm trees in the township and coconut trees flourish in the Narkelbagan area near the Rabindra Tirtha crossing where the Kolkata Gate has come up.

"Such trees can bend easily and their trunks don't snap during high winds," the official said.

A naturalist, however, said palm and coconut trees, though resilient to storms, do not offer any shade and that is an aspect that should be considered for avenue plantation.

The NKDA also plans to plant trees on barren stretches along the New Garia-Airport Metro route where trees could not be planted earlier because of construction work on the elevated corridor and stations.